62. Is That a Color Photo?

If you ask anyone in my family, they will tell you that I’ve always loved tricks. I like science tricks, magic tricks, and tricks on my little brother. This time we are going to trick your eyes by taking a black and white photo, and making your eyes tell your brain that the photo is in color. To do that, we are going to use something called retinal fatigue. The retina is a layer of light sensitive rod and cone cells at the back of your eye. The rod cells detect things that are light and dark, as well as movement. The cone cells detect color, and those are the cells that we are going to play with.

Lets start by looking at this red box. Stare at the black dot in the center, and try not to let your eyes wander. The red light from that box is hitting the cone cells in your retinas, causing the red sensitive cone cells to give off a chemical that stimulates nerve receptors to send a message to your brain that you are seeing red. After a few seconds, the chemicals start to deplete, so that part of your retina becomes less sensitive to red light. When you look at something white, that part of your retina sees white, minus some red, letting you see an after image that is a light blue color known as cyan. White light is made up of all the colors mixed together. Cyan is the color that you get if you take white light and remove the red part.

Every color has an inverse, a color that you mix it with to get white. Keep in mind that we are talking about mixing colors of light, not colors of paint. What color light do you think you would mix with this blue to give you white? Yellow. So this color yellow is the inverse of that color blue. You may have seen inverse images of flags that are green, yellow and black, instead of red, white and blue. We are going to take that a step farther.

Look at this picture, watching the numbers in the center. As you stare at the image, the cones in your retina are getting fatigued, becoming less sensitive to the colors they are seeing. By holding your eyes very still, you let specific areas of your retina become less sensitive to specific colors. When the numbers reach 30, the image will switch from these strange colors to the black and white photo that you saw at the beginning of this video, but because of retinal fatigue...for a few seconds, the image seems to be in color.

You just tricked your eyes into fooling your brain. If you think that I am tricking you instead, watch the video again. This time don’t stare at the numbers. Instead, move your eyes around the photo and at other parts of the screen. When the photo changes, you will see that it is truly just a black and white photo.

Have a wonder-filled week.